PubMed Health⌕ Search

Biomedical subjects

Katharina Grif

Publications and source records attributed to Katharina Grif.

9 recordsLinked to original sources

Emerging Shiga toxin-producing Escherichia coli serotypes in Europe: O100:H- and O127:H40.

Novel and as yet rare non-O157 Shiga toxin (Stx)-producing Escherichia coli (STEC) serotypes are emerging in Europe. Two different sorbitol-fermenting STECs, O100:H- carrying the virulence gene stx2 and O127:H40 carrying stx1 and eae genes (found in two related subjects), were isolated from patients' stool samples. Non-O157 STEC infections in humans are currently under-diagnosed. This report highlights the need for, and importance of, screening for Shiga toxins or serotypes other than just O157.

Aged↗

Prevalence, structure and expression of urease genes in Shiga toxin-producing Escherichia coli from humans and the environment.

A component of the ure gene cluster in E. coli, ureC, encodes a subunit of urease. We have investigated the distribution of ureC in 202 Shiga toxin-producing E. coli (STEC) strains from Austria belonging to 61 different serotypes. These strains were of human (n=150), animal (n=38), and food (n=14) origin. ureC was present in all 72 E. coli O157:H7 and O157:NM (non-motile) strains, as well as in all 29 strains of serotypes O26:H11/NM, O111:H8/NM and O145:NM. In contrast, none of eight sorbitol-fermenting E. coli O157:NM were ureC-positive. ureC occurred significantly more frequently among STEC that carry eae (113 of 132; 85.6%) than among eae-negative STEC strains (four of 70; 5.7%; p<0.0001). However, only 4 (2%) of the 202 strains (3.4% of ureC positive strains) expressed urease activity. There was no significant association (p=0.56) between urease expression and the source of the isolates (humans vs. animals). Nucleotide sequence analysis of PCR amplicons derived from all seven genes of the ure cluster in STEC of 10 different serotypes demonstrated a high degree of homology (>or=99%), indicating a recent acquisition of not necessarily expressed ure genes.

Adhesins, Bacterial↗

A comparison of Listeria monocytogenes serovar 4b isolates of clinical and food origin in Austria by automated ribotyping and pulsed-field gel electrophoresis.

In this study, two typing methods, automated ribotyping and pulsed-field gel electrophoresis (PFGE), were evaluated for the subtyping of Listeria monocytogenes serotype 4b. The strains originated from patients and food samples collected in Austria during 2001-2005 and from Europe and North America in the World Health Organization collaborative study on the subtyping of this species. The largest group of Austrian clinical isolates was of the same PFGE subtype as those isolated from foodborne outbreaks in Switzerland and in the United States. Another subtype of clinical isolates from Austria was indistinguishable to that obtained from isolates responsible for a foodborne outbreak in the United States in 1985. Although the discriminatory power of PFGE was higher than that of automated ribotyping, some PFGE types were differentiated by ribotyping. Thus, combining data obtained by both automated ribotyping and PFGE increases the strain discrimination. Still, many of the Austrian strains remain indistinguishable from strains of foodborne outbreaks in other countries although there is no known epidemiological relation. This complies to previous studies which show the highly clonal nature of L. monocytogenes 4b strains which are responsible for both large outbreaks and sporadic cases.

Animals↗

Cytolethal distending toxins in Shiga toxin-producing Escherichia coli: alleles, serotype distribution and biological effects.

To assess the prevalence of cytolethal distending toxin (CDT) among Shiga toxin-producing Escherichia coli (STEC), 202 STEC strains were investigated using PCRs targeting various cdt alleles (cdt-I to cdt-V). Seven of the 202 strains contained cdt-III and an additional seven contained cdt-V. All 14 cdt-positive strains produced biologically active CDT, as demonstrated by a progressive distension of cultured Chinese hamster ovary cells. The CDT-positive STEC belonged to eight different serotypes, including sorbitol-fermenting O157 : NM (non-motile). The data demonstrate that CDT is present in some STEC serotypes only. However, more studies are required to evaluate whether CDT presence is associated with severe disease.

Alleles↗

Identifying and subtyping species of dangerous pathogens by automated ribotyping.

An investigation of dangerous bacterial pathogens was conducted to determine the usefulness of automated rRNA operon ribotyping (RiboPrinter system) to identify species. A total of 26 isolates comprising Bacillus anthracis, Brucella spp., Burkholderia mallei, Francisella tularensis, and Yersinia pestis were tested using restriction endonucleases EcoRI, PstI, PvuII and AseI. The main problem was that the system's database-relying on EcoRI as restriction enzyme-does not contain the essential dangerous pathogens. B. anthracis was misidentified as B. cereus and Y. pestis as Y. pseudotuberculosis. Two isolates of F. tularensis ssp. holarctica were falsely identified as Vibrio cholerae. This study underscores that riboprint patterns generated with a single restriction enzyme are not always unique for each of the species tested. Using more than one enzyme, the RiboPrinter proved to be a valuable primary typing method. Databases of commercially available systems for the identification of bacteria should include the most important dangerous pathogens.

Austria↗

Hemolytic-uremic syndrome associated with enterohemorrhagic Escherichia coli O26:H infection and consumption of unpasteurized cow's milk.

BACKGROUND: Enterohemorrhagic Escherichia coli (EHEC) O26 has emerged as a significant cause of hemolytic-uremic syndrome (HUS). The source and the vehicle of contamination with EHEC O26 are not often identified. We report two Austrian cases of HUS due to E. coli O26:H- affecting an 11-month-old boy and a 28-month-old girl in which transmission through unpasteurized cow's milk was positively identified. METHODS AND RESULTS: Using automated ribotyping and pulsed-field gel electrophoresis (PFGE), the isolates (which yielded the virulence genes stx2, eae, and hly) were indistinguishable from each other. An epidemiologic investigation revealed that the children had stayed in the same hotel. Both patients had consumed unpasteurized cow's milk from the breakfast buffet. Fecal samples were taken from the cows of the farm producing the incriminating milk, and one of three cattle EHEC O26:H- isolates had a PFGE pattern indistinguishable from that of the patients' strains. CONCLUSIONS: These two cases of E. coli O26 infection illustrate the hazards associated with the consumption of raw milk, and underline the importance of microbiological diagnostic approaches able to detect sorbitol-fermenting, non-O157 EHEC.

Animals↗

Occurrence of Salmonella enterica serovar Dublin in Austria.

In Austria, Salmonella enterica serovar Dublin, a bovine-adapted serovar, rarely causes human infections. In the year 2000, Austria was within the European mean with an incidence of 0.1 per million inhabitants. Our data show that the vast majority of all Austrian serovar Dublin infections can be traced to two Tyrolian districts. This concentration of cases can be explained by a particularly traditional aspect of cattle farming in Tyrol, the alpine pasture. There is increased risk of cross-infection due to the communal keeping of animals from various farms. Infected cattle are a source of infection for people, and contagion usually occurs from eating beef and drinking cow's milk. Using pulsed-field gel electrophoresis and automated ribotyping, 3 out of 5 available isolates from human infections could be traced to characteristic Tyrolian S. Dublin clones. Bacteriological screening of herds with a known history of S. Dublin infection would be a start to prevent future contamination of alpine pastures through latently infected cattle excreting potentially infectious feces. Bacteriological screening for fecal carriage before the return of cattle from pastures known to be connected with infections could prevent cross-contamination of large mixed herds.

Adult↗

[Molecular characterization of Listeria monocytogenes and the significance for food hygiene].

Research on the pathogen Listeria monocytogenes is a key issue both for the clinical and the food microbiologist owing to the unique pathway of infection and the exposure of humans via contaminated foods. Although, in Austria, the incidence of listeriosis is about 870-fold lower than the incidence for Salmonella infection, the food law manages both foodborne pathogens with a comparable stringency. The current risk management is based on the assumption that environmental L. monocytogenes isolates, from which the pool of "foodborne" isolates is recruited, are of similar pathogenicity compared to clinical and outbreak isolates. This verdict became doubted in the recent years. Characterization of L. monocytogenes by virulence gene sequencing, virulence studies in vivo and in vitro and by molecular typing was considerably stimulating the discussion on virulence variability in L. monocytogenes. This article provides insights in the value of epidemiological follow-up studies by presenting a typing study on 15 cases of listeriosis observed in a district hospital in Turkey. Furthermore results from typing L. monocytogenes either by virulence gene sequencing, mismatch amplification mutation assay or by pulsed field gel electrophoresis are discussed. The close interaction of molecular microbiology with food microbiology both in applied and basic science is currently creating a new discipline of molecular food microbiology. We are convinced that veterinary medicine will contribute to this exiting development in a fruitful way.

Animals↗